1. Field of the Invention
The present invention relates to a so-called FIMS (front-opening interface mechanical standard), in which a pod is mounted and used when a wafer held within a transfer container called a pod is moved to a semiconductor processing unit in a semiconductor manufacturing process, and more in particular, it relates to a pod clamping unit for fixing the pod to the FIMS system, a pod corresponding to the unit, and a clamping mechanism and a clamping method using the unit in the FIMS system which is mounted with a pod called a FOUP (front-opening unified pod) and which transfers a semiconductor wafer to the pod.
2. Related Background Art
Heretofore, in general, the semiconductor manufacturing process has been performed within a so-called clean room, in which an interior of the room handling the semiconductor wafer is highly cleansed. However, in view of the enlargement of a wafer size and the cost reduction required for management of the clean room, in recent years, a system has been adopted where the interior of the processing unit, the pod (accommodation container of the wafer), and a micro space used for delivering a substrate from the pod to the processing unit alone are kept highly clean.
The pod comprises a shelf capable of holding a plurality of wafers in its interior in a parallel and spaced apart state, a main body portion having an approximate cubical form with an opening to be used for taking the wafer in and out at its one side, and a lid for closing the opening portion. The pod in which a formative surface of this opening portion is arranged not vertically below the pod, but on one side surface (front surface for the micro space) is named genetically the FOUP (front-opening unified pod), and the present invention mainly targets at a configuration using this FOUP.
The above-described micro space comprises a first opening portion facing a pod opening, a door for closing the first opening, a second opening provided at the semiconductor processing unit side, and a transfer robot for approaching the pod interior from the first opening portion to hold the wafer and transferring the wafer to the processing unit side by passing through the second opening. The configuration to form the micro space has at the same time a mounting board for supporting the pod in such a manner that the pod opening portion is placed in a correct position to a door front surface.
A positioning pin which is fitted in a hole for positioning provided in the pod bottom face and regulates a mounting position of the pod, and the clamping unit which is engaged with a clamped portion provided in the pod bottom face and fixes the pod to the mounting board are arranged on the upper surface of the mounting board. Usually, the mounting board is capable of moving back and forth for a predetermined distance in a door direction. When the wafer within the pod is to be transferred to the processing unit, the pod is moved until the pot lid contacts the door in a state of the pod being mounted, and after the contact, the lid is removed from the pod opening by the door. By these operations, the pod interior and the processing unit interior are communicated through the micro space, and subsequently, the transfer operation of the wafer is repeatedly performed. The mounting board, the door, the first opening portion, the opening and closing mechanism of the door, and the wall forming part of the micro space in which the first opening portion are formed is named generically the FIMS (front-opening interface mechanical standard) system.
The clamping mechanism in the FIMS system consists of an engaging concave portion having a clamped portion protruded toward the center of a concave portion as if to cover part of a concave opening portion, the concave portion being provided in the pod bottom face, and the clamping unit arranged in the mounting board side. As a conventional clamping unit, the configuration has been known, which is disclosed, for example, in Japanese Patent Application Laid-Open No. 2002-164412, U.S. Pat. No. 6,501,070B1 specification, and U.S. Pat. No. 6,281,516B1 specification. The clamping unit disclosed in Japanese Patent Application Laid-Open No. 2002-164412 is configured such that it swingably supports the center portion of an approximate bar-shaped member in which a latch claw is formed at its one end, and the other end is connected to an actuator. In this configuration, a mechanism is such that, by driving the other end by the actuator, the clamp portion is rotated, and the latch claw is engaged with the clamped portion of the pod. Further, the clamping unit disclosed in U.S. Pat. No. 6,281,516B1 specification is configured such that the latch claw rotating around an axial center is engaged with the clamped portion of the pod.
However, in the above described configuration, when the pod is to be fixed, the latch claw reaches a final stopping position while sliding on the clamped portion. Hence, there is high possibility that particles and like are generated, and in the FIMS system which extremely dislikes generation and existence of the particles and the like, this configuration has come to be out of use. In place of this configuration, in recent years, a configuration comprising a clamping unit shown below (see U.S. Pat. No. 6,501,070B1 specification) has come to be used.
In the clamping unit, a clamp member having an approximate T-shaped form is used. To be more specific, after the pod is placed on a predetermined position of the mounting board, the clamp member is lifted once, and after stopping within a swing space provided within the pod, turns 90 degrees, and after that, descends so as to engage with the clamped portion protruded as if to narrow a downward opening of the swing space. In this configuration, being different from the case of Japanese Patent Laid-Open No. 2002-164412, since there is no friction caused between the clamp member and the clamped portion surface, the particles and the like caused by this friction are sharply reduced.
The clamping unit disclosed in the U.S. Pat. No. 6,501,070B1 specification uses a rotary clamp cylinder and the like disclosed in Japanese Utility Model Application Laid-Open No. 5-52305. The rotary clamp cylinder, when an expandable and contactable piston rod changes from an expandable state to a shrunk state, has a direction of the piston rod in a flat surface vertical to the expandable and contactable axis turned 90 degrees. Actually, a clamp member is fixed on the upper portion of the piston rod and used. In a clamping operation, in a state of the pod being mounted on the mounting board, the clamp member protruded from the mounting board surface has already entered the engaging concave portion. By shrinking the piston rod from this state, the clamp member engages with the clamped portion, and the fixing of the pod is performed.
However, in the system disclosed in the U.S. Pat. No. 6,501,070B1 specification, a large swing space for allowing the T-shaped clamp member to rotate within the pod is required. This swing space has its opening narrowed by the existence of the clamped portion, and is a space not directly accessible when the cleaning and the like are to be performed. The existence of such a space difficult to access is not preferable in view of keeping a cleanliness factor of the pod.
By changing the T-shaped form into a form where a portion used for the clamp is protruded in one direction alone, the space difficult to access can be made small to a certain extent. Further, by so doing, the protruded portion on the mounting board surface can be also reduced. However, the rotary clamp cylinder used for this method is, because of its configuration, required to expand the piston rod at all the time with the pod being in a non-engaged state. Hence, when the pod is mounted on the mounting board, there is a fear of inviting a problem that the pod bottom face and the clamp member of the piston rod top end are brought into contact with each other prior to the pod positioning by the positioning pin, and the pod is given an unnecessary impact or the particles and the like expected not to generate by nature are generated.
The problem relating to this impact can be similarly generated even in the method disclosed in the U.S. Pat. No. 6,501,070B1 specification, where, because of the requirement of various configurations for rotation of the T-shaped clamp member or reason and the like for positioning by requirement of a large swing region, the T-shaped portion has no other choice but protrude on the mounting board surface. Further, the clamp member disclosed in the U.S. Pat. No. 6,501,070B1 specification adopts a configuration to move up and down accompanied with the movement of the mounting board, and even from this point, the clamp member is configured necessarily to protrude from the mounting board surface.
Further, in recent years, accompanied with the enlargement of the wafer size, the pod itself has been proceeding with its enlargement and the increase in its weight. Hence, the above described situation that might take place such as the unnecessary contact and collision between the clamp member and the pod bottom face, which were out of the question before, has been becoming actualized. In case the pod itself and all the weight of the wafer accommodated into it become heavy, there is high possibility that the above described unnecessary impact becomes large, and it is necessary to prevent such a situation from happening beforehand.
Further, accompanied with the enlargement of the pod and the increase in its weight, a load generated by inertia at the pod moving time and an impact generated at the wafer transfer time and the like also become large. In this case, the conventional clamping unit is relatively low in a capacity to fix the pod, and it is considered from now on that there arises a possibility of the mounting position of the pod being shifted by the application of some loads on the pod.
Further, in recent years, there have been demands aiming at allowing such a FIMS system to correspond to a so-called open cassette. However, to correspond to the current FOUP, it is inevitable and imperative to have a configuration where a protruding portion other than the pin for positioning exists on the mounting board surface. Hence, it is impossible to mount the open cassette on the mounting board as long as the FIMS system for the FOUP is concerned.